The objective of this proposal is to further elucidate those properties governing the fundamental chemistry of iron in heme-like environments. The synthesis of a number of new highly unsaturated 16-membered macrocyclic ligands and their iron complexes is proposed. Attempts will be made to produce 14,16 and 18 pi electrons systems within the inner macrocyclic rings which are free of the pyrole residues of porphyrins. Comparisons of their chemical and physical properties with porphyrins and heme complexes will be made. Electronic and molecular structures of the complexes will be examined primarily with the aid of electronic and nuclear magnetic resonance (H- and C13) spectroscopy as well as with three dimensional x-ray crystallography. The possibility of these ion complexes acting as electron transfer agents analogous to those of cytochromes will also be explored.